Various in-vehicle equipment remote control systems are proposed. One of such systems is an electronic key system. In this system, an ID code is checked by two-way communication between a portable electronic key and in-vehicle equipment. Based on the result of the checking, the status of doors, for example, a locked state or unlocked state, is controlled to change. Further, when a holder of the electronic key is in the vehicle compartment, releasing of the steering lock or starting of the engine is permitted.
In this electronic key system, predetermined detection areas are established inside and outside the vehicle. A request signal is sent out from the transmitters in the in-vehicle equipment in the detection areas at predetermined time intervals. Thus, the electronic key holder is constantly monitored when he/she approaches or gets in or out of the vehicle.
For example, the holder of the electronic key approaches the vehicle in an attempt to get in it, and enters one of the detection areas. In response to the request signal from the vehicle, the electronic key transmits a response signal to the in-vehicle equipment. On receipt of the response signal, the in-vehicle equipment further carries out communications with the electronic key in order to check whether the ID code of the electronic key matches with a previously registered ID code. Thus, the in-vehicle equipment acquires the ID code from the electronic key.
When the acquired ID code matches with the registered ID code, the in-vehicle equipment gives an in-vehicle door lock controller a control signal to bring the doors into the unlock standby state. When the electronic key holder touches a door handle after this state is established, the door lock controller detects that through a touch sensor or the like, and then unlocks the doors.
When the holder of the electronic key stops the vehicle engine and gets out of the vehicle, the detection area of the portable key moves from the inside to the outside of the vehicle compartment. In this case, when a door lock switch provided, for example, in proximity to a door handle is operated, the doors are locked.
According to the above electronic key system, the holder of the electronic key can lock and unlock the doors without manipulating the electronic key. This enhances the electronic key holders' convenience.
In this electronic key system, however, even when the vehicle has been parked, the in-vehicle equipment periodically performs the operation of detecting the electronic key. This increases its power consumption.